Scientists have worked out the maximum gravity humans could survive on another world, if we were to spread out into the universe.
Publishing their findings on the pre-print server arXiv, three scientists from the University of Zagreb in Croatia studied super-Earths in particular. And they found that our bodies could cope with about 4.5 times Earth’s gravity.
To come to this conclusion, the team had a rather unusual method, using Game of Thrones star and strongman Hafþór Júlíus Björnsson as a case study. They worked out what gravity “The Mountain” himself would be able to withstand, to calculate the maximum possible for a human.
They first looked at the gravitational force that the human body could endure, working it out to be about 90 times Earth gravity while standing still. For running, however, this dropped to about 10 times Earth’s gravity before bones started to break.
“Skeletal strength is pointless, however, if your muscles aren’t strong enough for you to stand up or walk,” Discover noted. “Based on squatting ability, [the team] calculated that at five times Earth’s gravity even an elite athlete wouldn’t be able to move from a seated position.”
This led to the analysis of The Mountain, who won the World’s Strongest Man competition in 2018. He’s about 2.06 meters (6 feet and 9 inches) tall and weighs more than 180 kilograms (400 pounds). And with all his strength, they found he could withstand about 4.6 times Earth’s gravity.
For us more regular puny humans, that drops to about three to four times Earth’s gravity. They do note that with a spacesuit or other technology it would be possible to withstand higher gravitational fields, but that might not be ideal for long-term colonization.
“Our calculations did not incorporate any suits or technology,” lead author Dr Nikola Poljak told Inverse. “With those, you could increase the limit we calculate immensely. However, it would not be very practical to walk around in a spacesuit your entire life.”
While interesting, the study is also important in terms of what planets we could consider truly habitable. Thousands of worlds have been found beyond our Solar System, some in the habitable zones of other planets, but many of which are super-Earths much more massive than our own.
“[I]t seems that, from the human perspective, the range of habitable planets is much narrower than the range of potentially life-supporting planets in the universe,” the team wrote in their paper. “This restriction arises primarily from gravity, as the only environmental factor which we cannot manipulate.”